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All light and no heat

Which is the more misguided use of public money: the NHS-funded homeopathy that the chief scientist has been railing against recently, or the government's subsidy for the current generation of solar panels? It's a tough one. Both divert cash from needier causes while making the middle classes feel slightly better. Forced to choose, however, the scientific mind might opt to keep funding homeopathy. Placebos do less damage in medicine than in green technology.

It's the most natural thing in the world to want to harvest energy from the sun. After all, the sun fires energy at the earth 8,000 times faster than we consume any and all forms of energy. So, it might seem surprising that experts gathered at the Royal Society on 14 November to discuss whether solar power has a future. There is no easy answer: while green plants have converted solar energy into chemical energy for 400 million years, if human beings are going to harvest the sun, we will have to do much better than "green" and "natural".

We look at nature and assume that billions of years of evolution have created plants with finely tuned systems for turning sunlight into energy. However, the average energy factory in a plant manages about 1 per cent energy conversion. The average solar cell on a roof does comparatively well, operating at 18 per cent efficiency.

But that is still not enough to be cost-effective. With the "feed-in tariff", a guaranteed rate for any electricity you generate and feed into the grid over the next 25 years, the government is, in effect, asking people to commit to keeping today's technology on their rooftops for decades. It's all very well pushing green initiatives, but the only thing the present solar fad will achieve will be to widen the gap between rich and poor. Those with higher disposable incomes can better afford to invest in solar-panel installation and take advantage of the high feed-in tariff on offer.

There's a north-south divide, too: it probably doesn't take a scientific mind to appreciate that, the tilt of the earth being what it is, southerners in the UK get more sunshine, and thus more electricity and income, from their system. Well-off southerners are reaping a disproportionate share of the feed-in tariff.

So long, solar

It wouldn't be so bad if these installations were making a big dent in carbon emissions. But the truth is that solar panels don't yet generate a lot of electricity. That is why those who gathered at the Royal Society don't see the current generation of solar panels as a solution for the long term. We need what one of the experts present has called "major, step-change advances".

The engineers working on those advances are hoping that natural photosynthesis is so inefficient because sunlight is so plentiful that plants need never do any better. The alternative is that evolving (and thus engineering) high-efficiency conversion of solar radiation is inherently difficult, and attempts to get there will hit a brick wall.

For the moment, we should be optimistic. Researchers are working on initiatives to concentrate solar power so that it can be harvested more efficiently. They are hatching schemes that will use the sun's energy to turn carbon dioxide into a usable fuel. And they are busy creating higher-efficiency materials that they hope will make future generations of solar panels a sensible investment.

There is every reason to think that the ideal future is indeed solar-powered. But let's be clear: despite what you might see on the south-facing rooftops of suburbia, this particular future hasn't arrived quite yet.

Michael Brooks's "Free Radicals: the Secret Anarchy of Science" is published by Profile Books (£12.99)